Social needs for robots have been increasing, and robots that communicate with humans have been developed. To start communication such as interaction, a robot needs to have mutual understanding for starting the communication with a target human who the robot is to communicate with.
Robots capable of locomotion (hereafter referred to as “mobile robots”), such as a humanoid robot with two legs and a wheeled robot, have also been developed. The use of a mobile robot that approaches a human to communicate with him or her has a safety problem, as there is a possibility that the robot collides with an obstacle. To solve the safety problem, Patent Literature (PTL) 1 discloses a technique for improving safety by allowing a human to visually recognize a dangerous range that varies as the operation of a mobile robot changes.
For stationary robots, too, there are techniques for drawing in a target human to be communicated with by, for example, outputting signal sound to attract his or her attention or outputting sound to call his or her name.